development of tantalum/tungsten boated electrothermal...

Development of Tantalum/Tungsten Boated Electrothermal Vaporization-Flame Atomic

Absorption Spectrometry and its Application for Quantitative Elemental Analysis

byYoung-Soo Cho

DEPARTMENT OF CHEMISTRYGRADUATE SCHOOL

CHANGWON NATIONAL UNIVERSITY

Development of Tantalum/Tungsten Boated Electrothermal Vaporization-Flame Atomic Absorption

Spectrometry and its Application for Quantitative Elemental Analysis

byYoung-Soo Cho

Under the Direction ofProfessor Yong-Ill Lee

A thesis Submitted to the committee of the Graduate School of Changwon National University in

partial Fulfillment of the requirements for the degree of Master of Science

2001. 12.December 2001

Approved by the committee of the Graduate School of

Changwon National University in Partial fulfillment of

the requirements for the degree of Master of Science

Thesis Committee : Chang-Soon Lee

Tae-Jin Won

Yong-Ill Lee

DEPARTMENT OF CHEMISTRY

GRADUATE SCHOOL

CHANGWON NATIONAL UNIVERSITY

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TABLE OF CONTENTS

LIST OF TABLES ········································································································· v

LIST OF FIGURES ······································································································ vi

1 INTRODUCTION ······································································································· 1

2 EXPERIMENTAL ······································································································· 9

2.1 ETV Chamber and Y-type connector ··················································· 9

2.2 Instrumentation ······························································································ 10

2.3 Reagents ············································································································ 11

2.3.1. Standard solution ················································································· 11

2.3.2. Solid sample ··························································································· 11

2.4 Operating procedures ················································································· 12

3 RESULTS AND DISCUSSION ········································································ 14

3.1 Optimization of the Parameters ···························································· 14

3.1.1 Optimization of ETV current ·························································· 14

3.1.2 Effect of argon carrier gas flow rate ······································· 15

3.2 Optimization for analysis of solid sample ······································· 16

3.2.1 The characterization of ETV current ········································ 17

3.2.2 Argon carrier gas flow rate efficiency ····································· 17

3.3 Analytical Performance ·············································································· 18

3.4 Application of Standard addition method for solid

materials of NIST, NIES ············································································ 19

4 CONCLUSION ·········································································································· 22

LITERATURE CITED ······························································································· 23

ABSTRACT ··················································································································· 26

ACKNOWLEDGMENTS ···························································································· 60

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LIST OF TABLES

Table 1. Instrumental condition of Flame Atomic Absorption

Spectrometry(A) and Electrothermal vaporization(B).

(Cu, Cd, Mn, Pb, and Zn with tantalum, and Co, Ni

with tungsten). ························································································ 28

Table 2. Physical properties of Mn, Cu, Zn, Cd , Pb, Co,

and Ni. ········································································································ 30

Table 3. Optimized ETV current of Mn, Cu, Zn, Cd , Pb,

Co, and Ni. ······························································································· 31

Table 4. Detection limits (3σblank, n=5), coefficient value,

and precision for Zinc, Cobalt, and Nickel of

ETV-FAAS. ······························································································· 32

Table 5. The reference concentration values of (A) NIST

and(B) NIES samples. ········································································· 33

Table 6. The analytical results of Mn, Cu, Zn, Cd and Pb

in food, biological and environmental samples with

linearity and relative standard deviation value in

percentage. ······························································································· 34

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LIST OF FIGURES

Fig. 1 Energy level diagrams for (a) absorption and (b) emission.

······························································································································ 2

Fig. 2 The scheme of electrothermal vaporization flame atomic

absorption spectrometry used in this study(ETV-FAAS).

···························································································································· 35

Fig. 3 The lighten filament of (A) Tantalum, and (B) Tungsten

at the vaporizing current. ····································································· 36

Fig. 4 The increasement of peak absorbance of Cu(A), Cd(B),

Mn(C), Pb(D), Zn(E) with tantalum (10ppm, 5μL) and Co(F),

Ni(G) with tungsten (10ppm, 3μL) according to the drying

and vaporizing current change. ······················································· 37

Fig. 5 The efficiency of argon carrier gas flow rate for ETV-

FAAS. ············································································································· 44

Fig. 6 Mg absorbance characteristic of ETV current in RM 8432

(Corn starch) ······························································································· 45

Fig. 7 The efficiency of argon carrier gas flow rate of Mg

in corn starch. ···························································································· 46

Fig. 8 Absorbance spectra and calibration curves of the element

(A) Zn, (B) Co, and (C) Ni. ································································· 47


(A)Zn in RM 8414 and RM 8415, (B) Mn in RM 8415 and

RM 8418, and (C) Cu in RM 8414 and RM 8415 by

standard addition method. ···································································· 50


(A) Mn and (B) Zn in NIES No. 3 by standard addition

method. ······································································································· 56


(A) Pb and (B) Cd in NIES No. 8 and No. 10 by standard

addition method. ···················································································· 58

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1 INTRODUCTION

Solids analysis utilizing a system to detect atomic

absorption or emission line continues to be a significant area

of research. A number of instrumental configurations were

used for the introduction of either slurried or solid samples

into flames, graphite furnaces and plasmas. In the absence of

external radiation, some analytes can be stimulated by

collisional processes, or by electrical or chemical energy,

and can emit photons when excited species return to

lower-energy states. The absorption and emission, which

are the most fundamental sections of many spectroscopic

phenomena including chemiluminescence, photoluminescence,

reflection and scattering, occur when external

electromagnetic radiation impinges upon a collection of

analyte species (atom, molecules, or ions) in a sample.

Absorption and emission process are illustrated in fig.

1-(a) and (b), respectively. The horizontal line labeled E0

corresponds to the lowest, or ground-state, energy and the

others labeled E1 and E2 are two higher-energy electronic

levels of the atom. Absorption of the incident photons by the

analyte, which is shown in fig. 1-(a), promotes the analyte

to an excited state. There are allowed transitions and

forbidden transitions. In the process are also transitions

between excited states (non resonant) but these are not

used in atomic absorption, thus restricting the number of

transitions (wavelengths in the ultraviolet and visible range)

that can be used for each element. Different atoms need

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different energies to be excited. This energy can be supplied

in many forms like flame and heating by electric current.

In fig. 1-(b), the promoted atom returns to the ground

state, emitting a photon whose frequency and wavelength.

The lights are often used as an emission source like plasma.

(a) (b)

E0 E0

E1

E2

E1

E2

(a) (b)

E0 E0

E1

E2

E1

E2

Fig. 1 Energy level diagrams for (a) absorption and (b)

emission.

In atomic absorption, the radiation is measured before

and after absorption and the amount absorbed is proportional

to the concentration of the analyte. Beer-Lambert law (a

combination of Beer's law and Lambert's law) mathematically

described the absorbance of light passing through a sample

solution (in atomic absorption-the atom population in the

flame) as a function of the length of the optical path through

the sample (length of the flame) and the concentration of the

absorbing species (ground state atoms).

I t= I 0 eεlc

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A= log I 0 / I t=εlc

,where A is the absorbance (or optical density), I0 the

incident radiation power, It the transmitted radiation power, ε

is absorptivity (absorption coefficient at the wavelength used

for the analysis), l the length of the absorption path, and c

the concentration of absorbing atoms. This equation means

that when analyzing the same type of atom (e.g. Cu) in

samples of unknown concentrations and standard solutions of

know concentration, where the absorptivity remains the same

and the absorption path (length of flame) remains the same,

the absorbance will be a linear function of the Cu

concentration. It should be linear but it is not always linear

throughout all the range of concentration. Hence, one cannot

rely upon mathematical calculations and analytical

measurements are made using calibration curves (though

work is essentially limited to the range where the calibration

lines are not too curved). There is no need to know the

values of ε and l as atomic absorption is a comparative

technique. One measures a set of standards of known

concentrations, prepares an absorbance vs. concentration

line and for each absorbance reading of samples with

unknown concentrations, finds the respective concentration

(in modern spectrometers this is done by the instrument's

computer). Atomic absorption spectrometers read the amount

of incident light without the sample and with the sample

(after absorption), compare them, and show the results in

absorbance units.[1]

Atomic absorption spectrometry (AAS) has been the most

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widely used method which is analytical technique for the

determination of minor, trace, and ultratrace metals in a

widely variety of complex samples such as environmental,

geological, and biological samples. AAS has also become

used in the analytical laboratory due to their many desirable

factors of low detection limits in the range of a few ppm,

ppb or less (atomization by flame and electrothermal

atomization), high sensitivity and selectivity, widespread

availability, modest cost per sample after initial set-up,

simultaneous or sequential multi-elemental determination,

good precision and accuracy, and ease of operation in an

analysis. The trace metal analysis can be carried out in the

presence of many other elements, usually, having an

advantage which makes the process simpler and saves a lot

of time and errors.

However, limiting factor in atomic spectroscopic

techniques, being universally accepted as an absolute method

of metal determination, is a sample introduction process and

system. A greater awareness for the development of sample

introduction process and technique to analyze various

samples has led to a subsequent increase in research

activity in this area. Ideally, the sample introduction system

for atomic spectroscopy would reproducibly and efficiently

transfer the sample to the atomization or excitation stage. It

should produce no interferences, be reproducible and

independent of the sample type, be universal for all atomic

spectroscopic techniques and have no memory or carry-over

effect.

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Electrothermal vaporization (ETV) is relatively new and

has proved to be a very useful technique for sample

introduction in various atomic spectrometry techniques

because of the higher transport efficiency of dry aerosols to

the atomizer, micro sampling capability, and the potential for

direct solid analysis.[2-3] The most common substrate used

for ETV is pyrolitically coated graphite. In a typical ETV

experiment, the sample is deposited on a graphite surface;

the process is consisted of drying, pyrolyzing, and

vaporizing. The gas-phase analyte is the interrogated by

atomic absorption spectrometry or the vaporized species are

transferred into the flame for the subsequent AAS detection.

The sample is always vaporized from the graphite surface,

and the interaction of various analytes with the graphite

substrate contributes to the sensitivity, the detection limits,

and the shape of the analytical signal.[4-5]

There were attempts to introduce matrix modifiers

which are included metallic materials for stabilizing high

temperature platform furnace, preventing analytes from

volatilizing, and increasing the volatility of sample matrix

.[6-12] However, it noted that chemical modifier should be

highly pure, and not caused spectral or chemical

interference.

In addition, refractory metal filaments such as

tungsten[13-15] or tantalum[16] had been used as furnace

materials instead of pyrolitic coated graphite. A boat-shaped

tantalum or tungsten filament vaporizer normally

manufactured belong to this group and have been applied as

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sample introduction part to AAS. The attraction of these

filaments is to be seen in their relatively low price, high

reproducibility, and physical property such as electrical

resistant due to high temperature. They form a simple,

inexpensive and efficient ETV device mounted in a small

pyrex glass apparatus, and sample volumes of up to 50 μL

can be loaded onto the boat with glass syringe.

Sample preparation is one of the critical factors

determining the quality of the analysis results. The analytes

were already largely dissolved in water, and required

minimum treatment for the subsequent stages of the chemical

analysis. If the analysis of solids are included in extended

scope, the extraction of the species of interest should have

to be considered.[17] In solid sample analysis, sample

preparation is often the most time consuming step and is

also considered involves some potential problems, such as

incomplete dissolution, precipitation of insoluble analyte and

loss of some elements during the heating. There has been

interest in and proposals for the analysis of ultratrace

metals in food, biological, and environmental

samples.[18-21] These kinds of solid samples are mostly

pretreated by concentrated acid which are HNO3, HF, HClO4,

HCl and H2O2, which are considered of the risk of sample

contamination. Recently microwave-assisted sample

dissolution has been employed extensively for shortening the

time required for sample dissolution, as well as to avoid

analyte losses and contamination. However, this commercial

microwave oven for analytical tasks has some main

- 7 -

drawbacks which are expensive, the short lifetime of the

digestion vessels operated under high pressures and

temperatures, the acid content left after the digestion, and

sample throughput is not very high.[22] The ideal method

for the analysis of solid samples is to eliminate the sample

dissolution, minimize the sample preparation and improve the

analytical results. Slurry sampling has been extensively used

for the analysis of solids[23-30] in order to simplify sample

preparation and to avoid some problems associated with

dissolution procedures. The success of slurry sampling

depends on some variables, such as the variance of the

sampled analyte mass, particle numbers and sizes[31]

present in the injected volumes, analyte homogeneity,

suspension medium, slurry concentration, stirring method and

sampling depth.

Calibration, standard addition, and internal standard

method have been tried for the determination of trace

element in solid samples, but standard addition method is

applied much more than others.

Standard addition methods are particularly useful for

analyzing complex samples in which the likelihood of matrix

effects is substantial. A standard addition method can take

several forms. One of the most common forms involves

adding one or more increments of a standard solution to

sample aliquots of the same size. This process is often

called spiking the sample. Each solution is then diluted to a

fixed volume before measurement. It should be noted that

when the amount of sample is limited, standard additions can

- 8 -

be carried out by successive introductions of increments of

the standard to a single measured volume of the unknown.

Measurements are made on the original sample and on the

sample plus the standard after each addition. In most

versions of the standard addition method, the sample matrix

is nearly identical after each addition, the only difference

being the concentration of the analyte or, in cases involving

the addition of an excess of an analytical reagent, the

concentration of the reagent. All other constituents of the

reaction mixture should be identical because the standards

are prepared in aliquots of the sample.[32]

The present work introduces a development of a tantalum

and tungsten filamented-ETV system connected to the

conventional acetylene/air FAAS system. Also it describes

evaluation of the performance of the system for the direct

determination of trace metal ions including linearity,

precision and detection limit. Standard addition method was

used for evaluating the quantitative capability of ETV on the

determination of Cu, Cd, Mn, Pb, and Zn in standard food

and environmental samples, and the analytical results were

compared to the certified reference values.

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2 EXPERIMENTAL

2.1 ETV Chamber and Y-type connector

Electrothermal vaporization assembly (ETV) was

respectively designed and manufactured of pyrex glass

chamber. The improved vaporizer unit (78.7 mm long) is

contained within an argon-filled enclosure. Tantalum and

tungsten boats which are fabricated from 0.025 and 0.05

mm-thick foil (Aldrich Chemical Co., USA) are mounted on

copper electrode terminals supported by a cylindrical pyrex

glass base (30 mm o.d) with a tangential gas inlet port and a

joint. This assembly is surrounded by a cylindrical pyrex

glass manifold. The conical top of the manifold contains two

ports. One port allows delivery of the sample to the tantalum

boat vaporizer surface, while the other permits the vaporized

sample to be swept by the injector gas into the flame.

The Y-type tube mentioned of transport efficiency in the

literature[16] was equipped between the flame and ETV

chamber for the connector. The right branch was connected

to the top of the ETV chamber, and the left to the auxiliary

oxidant gas inlet hose. Vaporized sample was mixed with the

auxiliary oxidant gas, and flew to the flame, then. To

decrease analyte loss in the transport process, the flexible

silicon tube was used as the transport tubing from the ETV

to the flame through Y-type connector. Using this design,

the sample vapor was directly penetrated to the transport

tube from vaporization chamber and then swept into the

flame by the stream of argon.

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2.2 Instrumentation

The ETV-FAAS shown in fig. 2 was constructed around

the following components, and the instrumental conditions

were shown in table 1. The system can be distinguished to

three parts, sample introduction, Y-type connector, and the

spectrometry. When the liquid or slurry samples loaded on

the metal filament were desolvated and vaporized in the

ETV, they were mixed with argon carrier gas. With auxiliary

gas, vaporized mixtures flew through Y-tube into the flame

and were analyzed. The atomic absorption measurements

were carried out using a Perkin Elmer 3300 atomic

absorption spectrometry (Perkin Elmer Co., Norwalk, CT)

with acetylene-air flame and a special hollow cathode lamp

for each metal element. Before all measurements were

performed, background correction of the hollow cathode lamp

was made with the spectrometry itself.

Tantalum (17×8mm) and tungsten (17×5mm) filament

were heated by supplying the electric current through

copper electrodes (88.5mm in length) by dc power supply

operated in constant voltage mode (max 50 V and 100 A,

Korea Switching Co., Seoul, Korea). The operating current is

supplied in step-mode which is changed automatically from

low to high value, and is optimized with respect to the

maximum peak height using the aqueous standard solutions.

Typical operating currents used in the experiments are 12～

20 A (about 170～480℃) up to 32 s for desolvation and 36～

68 A (about 1600～3500℃) up to 10 s for vaporization,

depending on the analyte element and sample matrix. The

- 11 -

current was controlled with a programmable current-timer

unit system designed in our laboratory.

The flow of argon carrier gas remained spiral in the

vaporizer chamber by forcing argon to flow tangentially

around the wall of the glass cone. The tangential flow cools

the glass wall and centers the vaporized samples with the

argon flow that remains spiral in the chamber. The argon

carrier gas flow rate was controlled with a Dwyer flow

meter and was typically 0.5～2.5 liters/min.

2.3 Reagents

2.3.1. Standard solution

Stock standard solutions of various elements (Cu, Cd,

Mn, Pb, Zn, Co, and Ni) of 1000 mg/L were prepared from

Aldrich atomic absorption standards.

Working standard solutions were prepared daily by

appropriate dilution of the respective stock standard

solutions. All solutions were prepared using high purity

deionized water (resistivity 18.2 MΩcm-1) from Milli-Q water

purification system (Millipore Corp., Molsheim, France).

2.3.2. Solid sample

The applicability of the method to real samples was

demonstrated by the analysis of the National Institute of

Standards & Technology (NIST, U.S.A) and the National

Institute for Environmental Studies (NIES, Japan) which are

RM 8414 (bovine muscle), 8415 (whole egg powder), 8418

(wheat gluten), and 8432 (corn starch) of NIST and No. 3

- 12 -

(chlorella), No. 8 (vehicle exhaust particulates), and No.

10-c (flourished rice) of NIES.

The powder samples were weight with microbalance and

were diluted with deionized water. They were warm up in

water for 1～2 hr with stirred, then the fine particles turned

to the slurry state. For the analysis of Mn and Zn in RM

8418 and NIES No. 3, the solid samples were pretreated

with acid digestion method because they were not dissolved

in deionized water at all. Nitric acid, hydrogen peroxide, and

chloric acid of analytical grade were added with 1～3 mL,

and the samples were digested in microwave oven with high

pressure and temperate. No. 8 and No. 10-c were used to

analysis directly of Pb and Cd. Cd for rice sample was

mixed with 50% (w/w) with standard solution of known

concentration, but Pb for vehicle sample was mixed with

0.01% (w/w) because of a high concentration of analyte.

These samples were dried in vacuum oven for 2 days at 5

0℃. Dried solid samples were grinded for their homogeneity.

The slurry sample was prepared with diluted ratio by

standard addition method which is known of the

concentration of added standard solution. At least the

sampling volume was 0.3 mL with micropipette which of the

volume was controlled digitally.

2.4 Operating procedures

For the manipulation of ETV-FAAS, the whole procedure

is as follows. Before the micro volume samples were loaded,

the metal filament was cleaned at the same current for

- 13 -

vaporizing with argon continuous flow. 3～10 microliter

standard solution samples loaded onto the filament through

the sample injection port using a Hamilton syringe were

initially desolvated by passage of approximately 16～20 A

current through the filament for 32 s. In the case of the

slurry sample prepared for a direct analysis of solid, 2～10

microliter was loaded onto the filament. All samples were

dried at 16 A for 32 s. After the drying step of the slurry

sample, dark brown ash were remained on the filament. At

this moment, the white smoke was found to fly through the

top of chamber. The argon carrier gas was about 1.5

liters/min rate during the desolvation and ashing. Final

vaporization of both aqueous standards and the slurry sample

was carried out by instantaneously raising the current to 52

A. At this time, adequate argon flow rate was preserved at

about 1.5 liters/min. The gaseous samples were flew into the

flame on the burner head mixed with the argon and

acetylene as auxiliary gas in the state of turning on flame,

and analyzed by FAAS.

- 14 -

3 RESULTS AND DISCUSSION

3.1 Optimization of the Parameters

Key operating parameters for ETV-FAAS, such as ETV

current and argon carrier gas flow rate were investigated for

optimization studies. As the vaporization and the excitation

of the analytes realized in two separate steps, the ETV

parameters were optimized successfully. For the most of the

sample in the state of solution and slurry, it found that 3～

10 microliter of stock solution and 2～10 microliter of solid

sample were adequate for these studies.

3.1.1 Optimization of ETV current

In principles, the volatilization of the sample was

performed by the resistive heating of the tantalum filament.

The filament was heated by supplying the electric current

through copper electrodes by dc power supply operated in

the constant voltage mode. The operating current was

optimized with respect to the maximum peak height for

various elements of the aqueous standard solution according

to the different volatility of elements. The physical and

chemical properties of the elements are shown in Table 2.

To optimize the ETV current, argon gas flow rate was set at

1.5 liter/min. The drying step was set at current of 12, 16 A

for tantalum boat and 16, 20 A for tungsten filament with the

holding time of 32 s. The vaporizing step was changed from

36 A to 68 A increasingly.

Fig. 3 shows the filament of tantalum and tungsten

- 15 -

lightening. Their currents were maximized at 52 and 64 A

respectively. The light of tantalum filament are much

brighter than that of tungsten.

The optimized ETV current is presented in Fig. 4. It is

the typical peak height variation of Cu, Cd, Mn, Pb, Zn, Co,

and Ni responses as a function of ETV current with 4 s

holding time. The variation of ETV currents from 36 A to 56

A by tantalum and from 56 A to 68 A by tungsten were

investigated and the all elements absorption signal reached

their maximum at 52 A and 64 A. The absorbance peak of

Co and Ni was not shown using tantalum boat but tungsten

because of the difference of electrical resistivity between

the metal filaments. Therefore, it can be guessed that the

temperature of the tungsten is higher than that of the

filament.

The effect of ETV current on the background signal was

evaluated because of depending on the amount of tantalum

and tungsten ablated from the filament during vaporization,

and the background intensity was little observed on

increasing the current.

From this evaluation, seven elements were chosen and

the optimized currents were determined from seven

elements. The optimized currents for these seven elements

are listed in Table 3.

3.1.2 Effect of argon carrier gas flow rate

The argon carrier gas flow rates of Co and Ni elements,

which were introduced to the ETV unit to carry the

- 16 -

vaporized sample into the flame, must be one of the most

important parameters in ETV-FAAS because of the transport

efficiency. The argon carrier gas flow rate from 1.0 to 2.5

liter/min was used. To optimize the argon carrier gas flow

rate, ETV current was set at 64 A for 4 s.

Fig. 5 shows the effect of the argon carrier gas flow

rate in a range of 1.0 to 2.5 liter/min on the peak height in

due consideration of background for Co and Ni loaded onto

tungsten filament (3 ㎕ of 10 μg/mL). Each element

absorption signal initiated with increasing of argon carrier

gas flow rate, reaches its maximum at 2.0 liter/min due to

the transport efficiency and decreases at higher flow rate.

For later investigations, argon carrier gas flow rate was held

constant at 2.0 liter/min for Co and Ni. Though higher gas

flow rates above 1.5 liters/min introduce more analyte into

the flame, the peak height was actually decreased in the

high flow rate by reducing the residence time of the analyte

in flame. In contrast, at low flow rates below 1.0 liters/min,

the signal peak becomes lower and broader in profile

because of increase diffusion of analyte in carrier gas.

3.2 Optimization for analysis of solid sample

To analyze trace elements in solid sample,

characterization must be performed about ETV current and

argon gas flow rate which give an effect for maximum

absorption signal intensity. These parameters were optimized

and 5μL of the slurry sample was tested in this study.

- 17 -

3.2.1 The characterization of ETV current

Corn starch was soluble in deionized water and was

warm up in water bath for 2 hr with stirring. 5 μL of slurry

corn starch sample was loaded onto tantalum boat-shape

filament by using cylinder. Before applying the ETV system

for solid analysis, it has been guessed that the sample like

corn starch can include complex matrix. Therefore, the study

of ETV current was performed varying vaporization current

from 32 A to 40 A.

Fig. 6 shows the Mg characteristic absorbance according

to the different ETV current. Slurry sample loaded on the

tantalum filament was not only desolvated but also ashed at

12 and 16 A for 32 s. Dried solid sample was dark brown

colored and all were transported to the flame at each

vaporization current. Mg element, which was performed at

285.2 nm as high concentration in corn starch, showed a

little bit higher absorbance at 52 A though the values were

similar.

3.2.2 Argon carrier gas flow rate efficiency

This carrier gas are employed for preventing the

filament oxidation and transporting the gaseous sample

efficiently which makes it possible that the peak broadening

can be avoided and the loss of sample also can be reduced.

That is to say, this parameter for highly efficient sample

transportation is very important.

Fig. 7 shows the effect of carrier gas flow rate for Mg

in corn starch slurry sample. The flow rate was changed

- 18 -

from 0.5 to 2.5 liter/min, and the sample volume was needed

about 5 μL repeating the drying (32 s) and vaporizing (4 s)

step. The Mg absorbance increased linearly and showed the

maximum flow rate at 1.5 liter/min. The average precision of

4.1 % RSD (relative standard deviation) was calculated from

five consecutive measurements of the peak height in this

experiment and the improved precision was obtained over

1.5 liter/min.

3.3 Analytical Performance

Under the selected operating conditions of ETV current

and argon carrier gas flow rate, linear calibration graphs

were obtained by using a constant volume. Fig. 8 presents

the absorbance spectra and the calibration graphs of Zn, Co,

and Ni with a volume of 10 and 3 μL in ranges of 5～100 ng

for Zn, 1.25～30 ng for Co, and 2.5～30 ng for Ni. The other

elements except Zn were tested by drawing calibration curve

in the literature [16], and cobalt and nickel which have

higher boiling points were employed to test the efficiency of

new filament tungsten in this study.

The numerical values were listed in Table 4 with a

coefficient linearity (r), reproducibility for five consecutive

firings yielded a %RSD, and the detection limits in the form

of absolute weight, ng. The standard deviation was

calculated from five consecutive measurements of the

absorbance using the peak height of each element. The

relatively good precision and lower detection limits may be

attributed to the stability of the whole system developed

- 19 -

which enabled efficient transport of the analyte aerosol,

optimization of gas flow rate, and proper temperature

programming for vaporization of analyte. The detection limits

were defined as the concentration of analyte that produces a

signal three times the standard deviation of the blank signal.

The blank signal was measured at the analytial line of the

element used in this work.

3.4 Application of Standard addition method for solid

materials of NIST, NIES

As mentioned in the experimental section, standard solid

materials were diluted with deionized water and were also

warm up in water bath. Only RM 8418 (Wheat gluten) was

pretreated by acid digestion method because this material

was not soluble in water 2～3 mLof the concentrated pure

acid such as mixed fluoric acid, chloric acid, hydrogen

peroxide and nitric acid may be used, and high pressure was

provided with polymer vessel in microwave oven for one and

a half hour. After digestion of the solid sample with acid,

the vessel should be cooled and the pressure in the vessel

should be drained. This is a tedious procedure taking very

long time for sample pretreatment.

With prepared sample through the upper method of solid

treatment, the quantitative analysis was performed with

standard addition method. The standard addition method has

been widely applied for the purpose of reducing matrix

effect which induces decrease of absorbance signal. It is

difficult to match sample complex matrix exactly if

- 20 -

calibration curve is used as a method for analysis of

unknown sample. However, the standard addition method can

be solved this problem because of adding the

concentration-known standard solutions, in the order of

increasing solution volume of the same concentration or

keeping different concentration of the same volume. When

the sample and standard solution are mixed, the complex

matrix are matched well.

In Table 5, the solid samples used in this study are

listed which are used in this study with the certificated

values. Most elements are copper, manganese, and zinc. Mg

in RM 8432 (corn starch) that was used for making sure of

the analysis ability by standard addition method. The solids

from RM 8414 to 8418 are food and biological samples which

are bovine muscle powder, whole egg powder, and wheat

gluten. NIES series were used as standard food and

environmental sample flourished rice, chlorella and vehicle

exhaust particulates.

The calibration curve and absorbance peak are shown in

fig. 9 and fig. 10 which are distinguished to NIST and NIES

samples. Blank test was performed for all elements to

determine absorbance degree by blank solvent, so that the

blank absorbance peak was removed from all spectra. The

calibration curve and linear-fitted line were graphed by

origin program, and the analysis value was calculated from

the graph considering dilution ratio. Following equation was

constructed for the calculation of unknown concentration of

solid samples.

- 21 -

Analytical results = (A- x)B

×(S+W)S

, where A is the y-axial absorbance obtained from

calibration curve, x is the absorbance of blank test, B is

equal to the slope magnitude, and S, W are the weight of

solid sample and deionized water.

The analysis of Pb, Co, Ni and Cd in NIES No. 8 and No.

10-c was applied with solid samples directly which are not

diluted or digested. Rice sample in complex matrix turned

into the dark brown ashes at drying current, 16A. Fig. 11

shows the absorbance peak and the calibration curves for Pb

and Cd. Tantalum-boat made it possible to analysis of solid

samples because the shape prevented them from being

dispersed. However, it was impossible to the analysis of Co

and Ni in NIES No. 8 as tungsten filament was not so

concave but flat that the powder was dispersed.

Table 6 summarizes the analysis of each element for

accuracy of the elemental determination. The accuracy of

the elemental determinations is evaluated by their standard

deviation from the reference value of the certified samples.

It follows from the results that the ETV system in the

present work has high accuracy and precision for the

quantitative analysis of Cu, Mn, and Zn in biological samples

of NIST , and Cd, Pb in NIES series as an environmental

solid.

- 22 -

4 CONCLUSION

Through the development of ETV-FAAS, an improved

ETV system using a boat and thin layer tantalum and

tungsten filament as vaporizer was successfully optimized to

give a high degree of reliability and flexibility. Argon carrier

gas of 1.5 and 2.0 liter/min, drying current of 16 and 20 A,

and vaporizing current of 40～52 and 64 A for copper,

cadmium, lead, manganese, zinc, cobalt, and nickel with

tantalum and tungsten, respectively, were achieved as

optimized conditions used for this system.

Not only the good detection limits for zinc, cobalt, and

nickel were obtained and adequate, and but also was

precision observed with this technique for its direct coupling

between ETV device and flame on burner head. That is,

detection limits in the range of 0.16 to 1.48 ng and good

precision of 3.19～3.87 %RSD for zinc, cobalt, and nickel

were obtained.

For a direct analysis of powder-type solid, the slurry

samples diluted with deionized water and undiluted powder

samples were prepared. They were mixed with a constant

volume standard solution to reduce matrix effect, and could

be analyzed in the ETV-FAAS system. The analysis results

were satisfied to the certificated values compared the

reference. The average relative standard deviation was 2.8～

5.5%RSD, and linearity coefficient showed highly good result.

- 23 -

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WILEY & SONS Publ.; Chichester; New York; 1994, p. 141.

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Anal. At. Spectro., 10, 55(1995).

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Spectrochimica Acta part B, 51, 1223(1996).

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- 25 -

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V. Alphen, and E. R. Denoyer, J. Anal. At. Spectro., 15,

389(2000).

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Food Chem., 48, 5781(2000).

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Douglas A. Skoog, F. James Holler, and Timothy A. Nieman;

Saunders Golden Sunburst Series; Philadelphia; 1998, p.

15-16.

- 26 -

ABSTRACT

Development of Tantalum/Tungsten Boated

Electrothermal Vaporization-Flame Atomic

Absorption Spectrometry and its Application

for Quantitative Elemental Analysis

by Young-Soo Cho

Department of Chemistry

Graduate School, Changwon National University

매트릭스가 복잡한 시료 속에 존재하는 미량의 중금속을 보다

쉽고 정확하게 분석하기 위한 방법으로서 전열증기-원자흡수분광기

가 널리 사용되어지고 있다. 전열증기화 장치는 원자분광분석기기의

시료도입장치로써 원자화장치로의 높은 시료전송효율과 미량시료에

대한 분석 가능성, 고체시료의 직접 분석에 대한 가능성을 가지고 있

으며, 특히, 시료에 포함되어 있는 용매에 대해 전원공급장치에서 제

공되는 전류세기를 조절하여 선택적인 탈용매화가 가능하므로 원자흡

수스펙트럼을 얻는데 있어서 방해가 되는 요인들을 잠재적으로 제거

할 수 있는 장점을 가지고 있다.

본 연구에서는 탄탈륨과 텅스텐을 이용한 전열증발장치를 직접

제작하여 미량원소를 분석하는데 있어서 최적조건을 얻기 위해 시료

를 전송하는 아르곤 기체의 최적유속과 각각의 금속원소들이 가지는

- 27 -

물리적 성질(녹는점과 끓는점)에 기초하여 시료의 탈용매화와 증기화

에 필요한 전류에 대해서 특성연구를 수행하 다. 이 실험을 통해 얻

은 최적 조건 하에서 미량 중금속 (Cu, Cd, Mn, Pb, Zn, Co, Ni)에

대한 검정곡선(Calibration curve)을 작성하여 선형성(Linearity)과

정 도(Precision), 검출한계(Detection limits)를 구할 수 있었다.

3∼10μL의 금속표준용액을 이용하여 Zn(5∼100 ng),

Co(1.25∼30 ng), Ni(2.5∼30 ng)의 범위 내에서 검정곡선을 작성

한 결과, 직선을 의미하는 1의 값에 가까운 선형계수값을 나타냄으로

써 선형성이 매우 좋고, 실험결과들을 통계적으로 처리하여 상대표준

편차를 백분율로 나타내었을 때 4% 이내임을 보 으며, 절대검출한

계가 각각 0.16, 1.48, 0.93 ng 임을 알 수 있었다.

표준물 첨가법에 의해 제조된 고체시료를 실제 정량분석에 적

용한 결과, 고체시료 속에 존재하는 Cu, Cd, Mn, Zn, Pb에 대한 결

과들이 모두 표준시료를 제조하는 기관에서 제공한 기준분석수치 내

에 포함됨을 확인할 수 있었다.

위의 최적화 연구를 통하여 전열증발장치를 이용한 불꽃원자흡

수분광법이 실제 매트릭스가 복잡한 고체시료의 분석에 적합하다는

것을 확인하 다.

- 28 -

Table 1. Instrumental condition of Flame Atomic Absorption

Spectrometry (A) and Electrothermal vaporization (B). (Cu,

Cd, Mn, Pb, and Zn with tantalum, and Co, Ni with tungsten).

(A)

Element Cu Cd Mn Pb Zn

Wavelength (nm) 324.8 228.8 279.5 283.3 213.9

Slit width (nm) 0.7 0.7 0.2 0.7 0.7

C2H2 : Air (L/min) 2 : 10 2 : 10 2 : 10 2 : 10 2 : 10

Lamp (mA) 15 4 20 10 15

Element Co Ni

Wavelength (nm) 240.7 232.0

Slit width (nm) 0.2 0.2

C2H2 : Air (L/min) 2 : 10 2 : 10

Lamp (mA) 25 30

- 29 -

(B)

Element Cu Cd Mn Pb Zn

Gas Ar Ar Ar Ar Ar

Flow rate (L/min) 1.5 1.5 1.5 1.5 1.5

Drying current (A) 16 12 12, 16 12 16

Drying time (sec) 32 32 32 32 32

Vaporizing current (A) 52 44 44, 52 44 40

Vaporizing time (sec) 4 4 4 4 4

Element Co Ni

Gas Ar Ar

Flow rate (L/min) 2.0 2.0

Drying current (A) 20 20

Drying time (sec) 32 32

Vaporizing current (A) 64 64

Vaporizing time (sec) 4 4

- 30 -

Table 2. Physical properties of Mn, Cu, Zn, Cd , Pb, Co, and

Ni.

Mn Cu Zn Cd Pb

Melting

point (K)1517 1357.6 692.7 594.2 600.6

Boiling

point (K)2335 2836 1180 1040 2023

Co Ni

Melting

point (K)1768 1726

Boiling

point (K)3201 3187

- 31 -

Table 3. Optimized ETV current of Mn, Cu, Zn, Cd , Pb, Co,

and Ni.

Element ETV current (A)Mn 48Cu 56Zn 40Cd 44Pb 44Co 64Ni 64

- 32 -

Table 4. Detection limits (3σblank, n=5), coefficient value, and

precision for Zinc, Cobalt, and Nickel of ETV-FAAS.

ElementDetection limit

(ng)

Coefficient value

(r)% RSD

Zn 0.16 0.99915 3.19Co 1.48 0.99942 3.53Ni 0.93 0.99931 3.87

- 33 -

Table 5. The reference concentration values of (A) NIST and

(B) NIES samples.

(A)

RMMinor and Trace Constituents (mg/kg)

Mg Zn Mn Cu

8414 - 142±14 - 2.84±0.45

8415 - 67.5±7.6 1.78±0.38 2.70±0.35

8418 - - 14.3±0.8 -

8432 31±5 - - -

(B)

Trace Constituents (μg/g)

Pb Cd Mn Zn

NIES

No. 3- - 69±5 20.5±1.0

NIES

No. 8219±9 - - -

NIES

No. 10- 1.82±0.06 - -

- 34 -

Table 6. The analytical results of Mn, Cu, Zn, Cd and Pb in

food, biological and environmental samples with linearity and

relative standard deviation value in percentage.

Element Sample typeRSD

(%)r

Analytical

result (mg/kg)

Mn

Whole egg powder

Wheat gluten

Chlorella

4.5

5.2

4.8

0.99600

0.99995

0.97720

1.52±0.07

15.0±0.8

71.36±3.43

CuBovine muscle powder

Whole egg powder

4.5

2.8

0.99570

0.98703

2.52±0.11

2.45±0.07

Zn

Bovine muscle powder

Whole egg powder

Chlorella

3.4

4.2

4.7

0.99726

0.99988

0.99620

143.01±4.86

63.3±2.7

20.0±1.0

Cd Flourished Rice 5.5 0.99912 1.84±0.10

PbVehicle exhaust

particulates5.4 0.99999 210±11

- 35 -

T e f lo n B a s e

P y r e x G la s s D o m e

S a m p le I n le t

+ -

S a m p le O u t l e t

A u x i l i a r y O x i d a n t I n le t

F lo w M e t e rA r g o n G a s O - r in g

F u e l I n l e t

D r a in

F la m e

P o w e r S u p p ly

T a n ta l u m F i la m e n t

E le c t r o d e

Fig. 2 The scheme of electrothermal vaporization flame

atomic absorption spectrometry used in this study

(ETV-FAAS).

- 36 -

(A) (B)

Fig. 3 The lighten filament of (A) Tantalum, and (B)

Tungsten at the vaporizing current.

- 37 -

0 .0

0 .1

0 .2

0 .3

0 .4

0 .51 2 A

4 0 4 4 4 8 5 2 5 6 6 0

Ab

sorb

ance

V a p o r iz a tio n C u rre n t (A )

0 .0

0 .1

0 .2

0 .3

0 .4

4 0 4 4 4 8 5 2 5 6 6 0

1 6 A

Ab

so

rban

ce


(A)

Fig. 4 The increasement of peak absorbance of Cu(A),

Cd(B), Mn(C), Pb(D), Zn(E) with tantalum (10ppm, 5μL) and

Co(F), Ni(G) with tungsten (10ppm, 3μL) according to the

drying and vaporizing current change.

- 38 -

0 .0 0

0 .0 5

0 .1 0

0 .1 5

0 .2 0

0 .2 5

0 .3 0

0 .3 5

1 2 A

3 6 4 0 4 4 4 8

Ab

so

rba

nc

e

V a p o r iz a t io n C u r r e n t (A )

0 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

0 .0 6

0 .0 71 6 A

3 6 4 0 4 4 4 8

Ab

sorb

ance


(B)

Fig. 4 (Continued).

- 39 -

0 .0

0 .1

0 .2

0 .3

4 0 4 4 4 8 5 2 5 6

Ab

sorb

ance


1 2 A

0 .0 0

0 .0 8

0 .1 6

4 0 4 4 4 8 5 2 5 6

Ab

sorb

ance

V a p o r iza tio n C u rre n t (A )

1 6 A

(C)

Fig. 4 (Continued).

- 40 -

0 .00 0

0 .00 5

0 .01 0

0 .01 5

0 .02 0

0 .02 5 12 A

40 44 48

Ab

sorb

ance

V a p o riza tio n C u rre n t (A )

0 .0 0 0

0 .0 0 5

0 .0 1 0

0 .0 1 5

0 .0 2 0

0 .0 2 51 6 A

4 0 4 4 4 8

Ab

sorb

ance

V a p o r iz a tio n c u rre n t (A )

(D)

Fig. 4 (Continued).

- 41 -

0 .0

0 .1

0 .2

0 .3

0 .4

0 .5

3 6 4 0 4 4 4 8 5 2

Ab

sorb

ance

C u r re n t (A )

1 2 A

0 .0

0 .1

0 .2

0 .3

3 6 4 0 4 4 4 8 5 2

Ab

sorb

ance

C u r re n t (A )

1 6 A

(E)

Fig. 4 (Continued).

- 42 -

0 .0 0 0

0 .0 0 5

0 .0 1 0

0 .0 1 5

0 .0 2 0

0 .0 2 5

0 .0 3 0

0 .0 3 5

0 .0 4 0

0 .0 4 5

5 6 6 0 6 4 6 8

Ab

sorb

ance

C u rre n t (A )

0 .0 0 0

0 .0 0 5

0 .0 1 0

0 .0 1 5

0 .0 2 0

0 .0 2 5

0 .0 3 0

0 .0 3 5

0 .0 4 0

0 .0 4 5

5 6 6 0 6 4 6 8

Ab

sorb

ance

C u rre n t (A )

(F)

Fig. 4 (Continued).

- 43 -

0 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

0 .0 6

5 6 6 0 6 4 6 8

Ab

sorb

ance

C u rre n t(A )

0 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

0 .0 6

5 6 6 0 6 4 6 8

Ab

so

rba

nc

e

C u r r e n t (A )

(G)

Fig. 4 (Continued).

- 44 -

0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

0.0160.0180.0200.0220.0240.0260.0280.0300.0320.0340.036

Ab

sorb

ance

F low -rate (L /m in)

C o N i

Fig. 5 The efficiency of argon carrier gas flow rate for

ETV-FAAS.

- 45 -

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

44A 48 A 52A

Ab

sorb

ance

V aporization C urren t (A)

16 A 12 A

Fig. 6 Mg absorbance characteristic of ETV current in RM

8432 (Corn starch)

- 46 -

0.5 1 .0 1 .5 2 .0 2 .50 .00

0.03

0.06

0.09

0.12

Ab

sorb

ance

F low -rate (L /m in)

Fig. 7 The efficiency of argon carrier gas flow rate of Mg

in corn starch.

- 47 -

0 2 4 6 80 .0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

Ab

so

rba

nc

e

T im e (s e c )

0 2 0 4 0 6 0 8 0 1 0 00 .0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

Ab

so

rba

nc

e

C o n c e n t r a t io n (n g )

(A)

Fig. 8 Absorbance spectra and calibration curves of the

element (A) Zn, (B) Co, and (C) Ni.

- 48 -

2 4 6 80 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

Ab

sorb

ance

T im e (s e c )

0 5 1 0 1 5 2 0 2 5 3 0 3 50 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

Ab

sorb

ance

C o n c e n tra tio n (n g )

(B)

Fig. 8 (Continued).

- 49 -

2 4 6 80 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

0 .0 6

0 .0 7

Ab

sorb

ance

T im e (s e c )

0 5 1 0 1 5 2 0 2 5 3 00 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

0 .0 6

0 .0 7

Ab

sorb

ance

C o n c e n tra tio n (n g )

(C)

Fig. 8 (Continued).

- 50 -

2 4 60 .0 0

0 .0 4

0 .0 8

0 .1 2

0 .1 6

0 .2 0

0 .2 4

Ab

sorb

ance

T im e (s e c )

- 2 . 5 - 2 . 0 - 1 . 5 - 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0

0 . 0 5

0 . 1 0

0 . 1 5

0 . 2 0

0 . 2 5

Ab

so

rba

nc

e

C o n c e n t r a t i o n ( p p m )

(A)


element (A)Zn in RM 8414 and RM 8415, (B) Mn in RM 8415

and RM 8418, and (C) Cu in RM 8414 and RM 8415 by

standard addition method.

- 51 -

2 4 60 .0 00 .0 50 .1 00 .1 50 .2 00 .2 50 .3 00 .3 50 .4 00 .4 50 .5 00 .5 5

Ab

so

rba

nc

e

T im e (s e c )

-4 -3 -2 -1 0 1 2

0.1

0.2

0.3

0.4

0.5

0.6

Ab

sorb

ance

C oncentra tion (ppm )

(A)

Fig. 9 (Continued).

- 52 -

2 4 60 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

Ab

sorb

ance

T im e (s e c )

- 2 - 1 0 1 2 3 4 5

0 . 0 1

0 . 0 2

0 . 0 3

0 . 0 4

Ab

so

rba

nc

e

C o n c e n t r a t io n ( p p m )

(B)

Fig. 9 (Continued).

- 53 -

2 4 60 .0 0

0 .0 1

0 .0 2

0 .0 3

Ab

sorb

ance

T im e (s e c )

- 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5

0 . 0 0 5

0 . 0 1 0

0 . 0 1 5

0 . 0 2 0

0 . 0 2 5

0 . 0 3 0

0 . 0 3 5

Ab

so

rba

nc

e


(B)

Fig. 9 (Continued).

- 54 -

2 4 60 .0 0

0 .0 1

0 .0 2

0 .0 3

Ab

sorb

ance

T im e (s e c )

- 0 . 6 - 0 . 3 0 . 0 0 . 3 0 . 6 0 . 9 1 . 2 1 . 5

0 . 0 1

0 . 0 2

0 . 0 3

Ab

so

rba

nc

e


(C)

Fig. 9 (Continued).

- 55 -

2 4 60 .0 0

0 .0 1

0 .0 2

0 .0 3

0 .0 4

0 .0 5

Ab

sorb

ance

T im e (s e c )

- 0 . 4 - 0 . 2 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 1 . 2

0 . 0 1

0 . 0 2

0 . 0 3

0 . 0 4

0 . 0 5

Ab

so

rba

nc

e


(C)

Fig. 9 (Continued).

- 56 -

2 4 6 80 .0 0 0

0 .0 0 5

0 .0 1 0

0 .0 1 5

0 .0 2 0

0 .0 2 5

0 .0 3 0

Ab

sorb

ance

T im e (s e c )

- 2 - 1 0 1 2 3 4 5 6 7

0 . 0 0 5

0 . 0 1 0

0 . 0 1 5

0 . 0 2 0

0 . 0 2 5

0 . 0 3 0

0 . 0 3 5

Ab

so

rba

nc

e


(A)


element (A) Mn and (B) Zn in NIES No. 3 by standard

addition method.

- 57 -

2 4 6 80 .0

0 .2

0 .4

0 .6

0 .8

Ab

so

rba

nc

e

T im e (s e c )

- 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0

0 . 2

0 . 4

0 . 6

0 . 8

Ab

so

rba

nc

e


(B)

Fig. 10 (Continued).

- 58 -

2 4 60 .0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 .7

0 .8

0 .9

1 .0

1 .1

1 .2

1 .3

1 .4

Ab

so

rba

nc

e

T im e (s e c )

- 2 - 1 0 1 2 3 4 5 6 7

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

Ab

so

rba

nc

e


(A)


element (A) Pb and (B) Cd in NIES No. 8 and No. 10 by

standard addition method.

- 59 -

2 4 60 .0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 .7

0 .8

Ab

sorb

ance

T im e (s e c )

- 1 . 0 - 0 . 5 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0

0 . 1

0 . 2

0 . 3

0 . 4

0 . 5

0 . 6

0 . 7

Ab

so

rba

nc

e


(B)

Fig. 11 (Continued).

- 60 -

ACKNOWLEDGMENTS

어느덧 제게도 학부시절부터 대학원까지 화학과와 맺은 인연의 시

간들을 정리할 때가 다가왔습니다. 참으로 많은 경험들을 통해서 제

자신이 좀더 나은 방향으로 발전될 수 있었던 소중한 시간들이었다고

느끼고 있습니다. 이제 그 동안 제게 도움을 주신 모든 분들께 이 지

면을 빌어 감사의 인사를 전하고자 합니다.

먼저, 부족함이 많은 저에게 연구뿐만 아니라 여러 가지 면에서

신경을 써주시고 도움을 주신 이용일 교수님께 진심으로 감사드립니

다. 그 동안 제게 해주신 긍정적이면서도 발전적인 조언들이 마음 속

깊이 새겨져 잊혀지지 않을 듯 싶습니다. 그리고 화학과의 제일 어른

이시고 학생들 뒤에서 묵묵히 지켜봐 주시는 백건호 교수님과 따뜻하

고 자상한 마음으로 학생들을 격려해 주시는 이창순 교수님, 이민주

교수님, 투박하지만 정겨운 어투로 편안하게 대해주시는 안철진 교수

님, 소탈한 모습이 잘 어울리시는 원태진 교수님, 지금은 바쁜 연구활

동 때문에 미국에 계시는 멋스러운 유 재 교수님, 넉넉한 웃음이 좋

아 보이시는 신동수 교수님께 감사드립니다.

오랜 실험실 생활을 통하여 제가 즐겁게 학교생활을 할 수 있도록

도움을 주신, 그리고 조언을 아끼지 않으시던 김미경 박사님과 자신

의 일에 항상 최선을 다하는 강신봉 선배님, 의욕으로 가득한 모습이

인상적이던 유학생 1호 김재국 선배님, 호탕한 웃음 때문에 인기가

많은 최종수 선배님, 장난을 많이 쳐도 기분좋게 받아주던 김 욱 선

배님, 차분함과 꼼꼼함으로 똘똘 뭉친 임재민 선배님과 그의 아내가

되어 타국에서도 현명함으로 잘 지낼 박성하 선배님, 항상 웃음 짓고

다닌다 하여 방 이로 통하던 조효현 선배님, 특이한 유머감각으로

많은 사람들에게 웃음을 제공하던 김 주 선배님, 말수는 적지만 마

- 61 -

음이 참 따뜻한 이선 선배님, 방장으로서 최선을 다하고 있는 김상

득 선배님, 새내기 대학원생으로서 더욱 연구에 정진할 이원배 선배

님과 이수경 후배님, 갓 실험을 시작하여 서투름이 많을 강종필 선배

님과 학부동기인 박승건, 이태희 학우님께 감사드립니다.

같은 시기에 대학원에 진학하여 여러모로 신경을 많이 써주었고,

사회에 나가서도 자신의 위치에서 변함없이 최선을 다하여 생활할 변

기환 선배님과 한상윤 선배님, 그리고 같은 사무실에 있으면서 여러

가지로 도움을 많이 준 박주희 선배님께 진심으로 감사드립니다. 또

한, 언제나 제 뒤에서 묵묵히 지켜보면서 격려해 준 우 희 님, 조미

희 님, 신희경 님에게도 감사드립니다.

마지막으로, 이 날까지 올바른 정신으로 성실하고 정직하게 살도

록 가르쳐주신 부모님과 동생을 아끼는 마음으로 질책도 마다하지 않

던 언니, 오빠께 감사드립니다. 항상 건강하시고 행복하시기만을 바랄

뿐입니다. 그리고 저에 대한 굳은 믿음이 실망으로 바뀌지 않도록 더

욱 열심히, 부지런히 살겠습니다.

development of tantalum/tungsten boated electrothermal...

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